#include<stdio.h>
#include<conio.h>
#include<math.h>
int main(){
    char ch;
    printf("\nnhap vao 1 ky tu: ");
    scanf("%c",&ch);
    if(ch>=65 && ch<97 ){
    	ch=ch+32;
    	printf("\nky tu vua nhap:\t%c ",ch);
    }
    else if(ch>=97){
    	ch=ch-32;
    	printf("ky tu vua nhap:\t%c",ch);
    }
getch();
}
